1. Field of the Invention
The invention relates to a drive device for motor vehicle sliding sunroofs.
In particular, the invention relates to a drive device for motor vehicle sliding sunroofs, having a rotatable toothed pinion, which can be driven in both directions of rotation, and two flexible drive cables each provided with a helical wire working winding, which are displaceably guided opposite one another in parallel guide channels where they are rigid in compression, the rotatable toothed pinion being arranged between the two flexible drive cables, each with a helical working winding for converting its rotational movements into opposing displacement movements of said cables.
For the purposes of the present invention the term xe2x80x9cmotor vehicle sliding sunroofxe2x80x9d or xe2x80x9csliding sunroofxe2x80x9d is intended to include all design constructions in which at least one cover is adjustably fitted to a roof opening of a motor vehicle and is moveable by means of the drive device. This includes not only design constructions in which the cover, after lowering of its rear edge, is displaceable under the rear fixed roof surface in order to expose the roof opening, but also so-called tilt-or-slide sunroofs, in which the cover, starting from the position in which it closes the roof opening, can also be swivelled about a swivel axis provided in proximity to its front edge for deployment above the fixed roof surface. Finally this definition is also intended to encompass those design constructions in which the cover, after raising of its rear edge, can be displaced rearwards to a greater or lesser extent above the rear fixed roof surface (so-called top-ridge sliding sunroofs, spoiler roofs). Roof design constructions should also be included, in which the minimum of one cover is formed not only from sheet metal or glass, but also as a folding roof made from flexible material.
2. Description of the Related Art
A common feature of all known drive devices of the type referred to in the introductory part (for example, DE 38 03 816 A1, DE 38 09 949 A1, DE 195 31 514 C1) is that the toothed pinion driven by way of hand crank mechanism or an electric geared motor meshes by means of its toothing directly with the working windings of the drive cables in the manner of a rack drive mechanism. Owing to the circular cross-sectional circumference of the wire working winding and the unavoidable dimensional tolerances on the drive cables, the toothed pinion and the guide elements for the drive cables, in these known drive devices it is not possible to achieve an ideal tooth form on the toothed pinion, which would correspond to a normal, optimised gear mechanism. Furthermore it is not possible to ensure that at least one tooth of the toothed pinion meshes with each drive cable at all times, which results in jerky, unequal feeding of the drive cables. At the same time the effective circle of the toothed pinion varies owing to play in the tooth engagement and also due to deflection movements of the drive cable, as a result of which vibrations may be induced that can be transmitted to the frame structure of the sliding sunroof and hence to the vehicle roof itself. This may result in the generation of disturbing noise in adjustment and drive movements of the sliding sunroof, especially when the toothed pinion is driven by an electric motor.
The object of the invention is to provide a drive device of the type referred to in the introductory part, which will permit equal and quiet displacement movements of the two drive cables without inducing vibrations.
According to the present invention, there is provided a drive device for motor vehicle sliding sunroofs, having a rotatable toothed pinion, which can be driven in both directions of rotation, and two flexible drive cables each provided with a helical wire working winding, which are displaceably guided opposite one another in parallel guide channels where they are rigid in compression, the rotatable toothed pinion being arranged between the two flexible drive cables, each with a helical working winding for converting its rotational movements into opposing displacement movements of said cables; wherein an endless, flexible, toothed belt of high tensile strength is arranged between the rotatable toothed pinion and the two flexible drive cables, the endless, flexible, toothed belt having an inner side on which is provided a complementary internal toothing to the toothing of the rotatable toothed pinion and having an outer side on which is provided a complementary external toothing to the helical working windings of the drive cables; wherein the endless, flexible, toothed belt partially wraps the rotatable toothed pinion and its internal toothing is held in constant frictional engagement with the toothing of the rotatable toothed pinion; and wherein the toothed belt has opposing line sections which are guided parallel to the drive cables and its external toothing on the opposing line sections is held in constant frictional engagement with the working windings of the two flexible drive cables.
The arrangement of a toothed belt in accordance with the invention decouples toothed pinion and drive cable from one another, a majority of teeth of the toothed pinion being in meshing engagement with a majority of teeth of the internal toothing of the toothed belt at all times and a majority of teeth of the external toothing of the toothed belt being in meshing engagement with a majority of succeeding sections of the wire working windings of the two drive cables at all times. In this way a smooth, equal and virtually silent displacement drive of the two drive cables is obtained.
The internal toothing of the toothed belt and the toothed pinion can be in this context advantageously straight-toothed, whilst the external toothing of the toothed belt is helically toothed corresponding to the thread-like helical lead of the wire working winding of the drive cables. The straight toothing of toothed pinion and internal toothing of the toothed belt allow this tooth engagement to be optimised. The external toothing of the toothed belt readily conforms to the thread-like working winding and ensures an engagement free from play, especially since a majority of teeth of the external toothing here mesh with the working windings of the drive cables at all times along rectilinear line sections.
A number of embodiments are envisaged for reversal of the endless toothed belt after the rectilinear and parallel line sections following the toothed pinion partially wrapped by the toothed belt, on which line sections the external toothing of the toothed belt meshes with the working windings of the drive cables.
The toothed belt may be reversed on a pivoted sheave, resulting in minimal friction losses. The sheave may have a toothing corresponding to the toothed pinion, that is to say a further toothed pinion matching the drive toothed pinion may also be used as return sheave, which is itself, however, not independently driven but is only driven to rotate by the driven toothed belt. In this embodiment there is no need for the manufacture of an additional part, that is a non-toothed return sheave.
Instead of a toothed or non-toothed return sheave, however, rounded slide surface may be used, over which the toothed belt is guided, if the slide surface is accordingly matched to the material of the toothed belt in terms of a low coefficient of friction.
The arrangement is advantageously configured so that in the area of the line sections intended for the engagement of its external toothing with the working windings of the drive cables, the toothed belt is guided so that it slides on support surfaces. This measure ensures tooth engagement between the external toothing of the toothed belt and the working windings of the drive cables under all operating conditions.
To simplify the design construction of the drive device, the pivoted sheave or the slide surface and the support surfaces for the toothed belt may be arranged on a support and guide element fixed between the two drive cables. In the case of an electric motor drive, the said support and guide element may be an integral part of the motor/transmission unit.
In an advantageous development of the drive device it is proposed that the tension of the toothed belt be adjustable by means of a tensioning device. Alternatively, however, the arrangement may also be configured so that the tension of the toothed belt is produced by a spring-loaded tensioning device. In this case no adjustment operations are necessary. Furthermore it is ensured in series production and in mass production that if the same springs are used the same tension is imparted to the toothed belts from one drive device to another.
In both alternative arrangements the tensioning device may be operatively connected to the pivoted sheave or the rounded slide surface, that is to say in adjustment of the belt tension or by means of spring force it may exert a displacing action directly on the sheave or the slide surface.
In one embodiment of the tensioning device, this has a tensioning slide, guided so that it is capable of sliding on the support and guide element parallel to the drive cables, on which guide the sheave is supported or the rounded slide surface is fixed. In the case of an adjustable tensioning device design, an adjusting eccentric cam may be provided, fixed to the support and guide element so that it is both rotatable and lockable, the cam bearing on the tensioning slide on that side of the tensioning slide remote from the sheave or the slide surface. When the toothed belt is to be tensioned by spring force, a biased compression spring may be arranged between the support and guide element and the tensioning slide.